BZOJ1954 Pku3764 the Xor-longest Path

"The classic application of Trie"-by Hzwer

We write down the XOR value of each point to the root and find out the maximum of two XOR values (because (a ^ c) ^ (b ^ c) = a ^ b)

So use Trie to write down each number of bits, each query when using greed, trying to go to another son can.

1 /**************************************************************2 problem:19543 User:rausen4 language:c++5 result:accepted6 time:360 Ms7 memory:27368 KB8 ****************************************************************/9  Ten#include <cstdio> One#include <algorithm> A   - using namespacestd; - Const intN =100005; the   - structEdge { -     intNext, to, V; - Edge () {} +Edgeint_n,int_t,int_v): Next (_n), to (_t), V (_v) {} -} e[n <<1]; +   A intfirst[n], tot; at   - structTrie_node { -     intson[2]; -} t[3000005]; -   - intCnt_trie =1, root =1; in   - intN, ans; to intV[n], a[ +]; +   -InlineintRead () { the     intx =0, SGN =1; *     CharCH =GetChar (); $      while(Ch <'0'||'9'<ch) {Panax Notoginseng         if(ch = ='-') SGN =-1; -CH =GetChar (); the     } +      while('0'<= CH && Ch <='9') { Ax = x *Ten+ CH-'0'; theCH =GetChar (); +     } -     returnSGN *x; $ } $   - voidAdd_edges (intXintYintz) { -E[++tot] = Edge (first[x], y, z), first[x] =tot; theE[++tot] = Edge (First[y], x, z), first[y] =tot; - }Wuyi   the voidDfsintPintFA) { -     intx, y; Wu      for(x = first[p]; x; x =e[x].next) -         if((y = e[x].to)! =FA) { AboutV[y] = v[p] ^e[x].v; $ dfs (y, p); -         } - } -   A voidInsertintx) { +     intNow, I, cnt_a =0; the      for(i =0; I <= -; ++i) -A[i] = x &1, x >>=1; $Reverse (A, A + to); thenow =Root; the      for(i =0; I <= -; ++i) { the         if(!t[now].son[a[i]]) t[now].son[a[i]] = + +Cnt_trie; thenow =T[now].son[a[i]]; -     } in } the   the intQueryintx) { About     intNow, I, cnt_a =0, res =0; the      for(i =0; I <= -; ++i) theA[i] = x &1, x >>=1; theReverse (A, A + to); +now =Root; -      for(i =0; I <= -; ++i) { the         if(T[now].son[!a[i]]) now = T[now].son[!a[i]], res + = (1<< --i);Bayi         Elsenow =T[now].son[a[i]]; the     } the     returnRes; - } -   the intMain () { the     intI, x, Y, Z; then =read (); the      for(i =1; I < n; ++i) { -x = Read (), y = read (), z =read (); the add_edges (x, y, z); the     } theDfs1,0);94      for(i =1; I <= N; ++i) the Insert (V[i]); the      for(i =1; I <= N; ++i) theAns =max (ans, query (v[i]));98printf"%d\n", ans); About     return 0; -}

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BZOJ1954 Pku3764 the Xor-longest Path